1) Field of the Invention
The field of this invention relates to bicycle frames and more particularly to a bicycle frame which is designed to be of high strength and yet aerodynamically slippery to achieve high performance.
Conventional bicycle frames are built from individual tubes which are secured together by welding, brazing or using other means for joining the tubes. The individual frame tubes are designated by their location in relation to the major components making up the functioning bicycle. The short frame tube which supports the handle bar assembly and the front fork was referred to as the head tube. The tube which supports the seat and connects to the pedal axle support was referred to as the seat tube. The tube which joins the seat tube and the head tube is referred to as the top tube. The tube which descends from the head tube to the pedal hub is called the down tube. The pair of tubes which descend from the seat tube to the rear wheel axle have been referred to as the rear wheel support tubes, one vertical and one horizontal.
Because of the multiplicity of connections required to secure separate tubes in connection with the bicycle frame, it is important to ensure that the welding or other similar type of securement was accomplished most proficiently. Also, it is necessary to construct the bicycle frame of extremely strong tubing and therefore in the past it has been common to utilize round steel tubing.
Within the past several years, bicycle racing has become a common activity for a great number of people. Bicycle racers are always looking for an improvement in the construction of the bicycle which would give that racer an edge over the competition. One particular edge would be if the bicycle frame could be constructed to be a lighter weight but yet maintaining its high strength characteristics. To achieve this end result, bicycle frames have been constructed out of exotic materials such as titanium. However, the use of exotic materials is expensive and not everybody can afford such materials.
One type of material of construction that is light in weight would be aluminum. However, in the past, aluminum has not provided sufficient strength to be used effectively in conjunction with a bicycle frame. The main problem with aluminum is that the bicycle frame incurs wobble or vibration during usage which induces a rough ride which would be poor ride when used in conjunction with a racing bicycle.
Another way in which an edge can be had in conjunction with a racing bicycle is by designing of the tubular members of the frame to be aerodynamic so as to make them slippery as they move through the wind. It has been known in the past to construct bicycle frame members having a general teardrop configuration. The length of the tube in the direction of movement through the air is substantially longer than its width. For structural strength reasons about the best length to width ratio that could be obtained was two to two and a half to one. It has been known that a far better ratio would be around three and one half to one. However, prior to the present invention it has not been possible to design a bicycle frame of sufficient strength that would have the ratio of around three and a half to one.